QR codes, short for Quick Response codes, are starting to get popular these days.
QR codes are similar to bar codes that we see everyday on consumer products but the difference is that the usual bar codes are only linear one-dimensional codes which can only hold up to 20 numerical digits, while QR codes are two-dimensional (2D) matrix codes that can accommodate thousands of alphanumeric characters or data.
This fact alone proves that QR code has so much potential to do anything :p.

How QR codes work

QR codes are scanned with mobile devices like iPhone, Android, or other camera enabled Smartphones with easily downloadable apps from the Market.
With QR codes, you can link users to your site’s URL, download content, activate phone functions and easily connect the mobile device to the internet. And you can even insert custom texts as well.

So how do you generate QR codes?

There a numerous QR code generators around. I personally use Kaywa just simply because it's simpler :p

Practical applications of QR codes

There are many ways you can use QR codes. Here are some of the most common applications for QR codes these days.

1. Business cards
2.  Corporate or product brochures and other marketing
3. Posters and announcements
4. Product packaging and tags
5. Signages and billboard ads
6. Clothes (QR codes printed on shirts are a big hit these days)
7. Magazine or newspaper ads
8. Website, email or any online campaign
9. Name tags
10. Books

Designer QR codes

QR codes doesn’t have to look boring. You can design QR codes outside its black and white mazed like box. QR codes are very potential marketing tools, and presenting visually appealing QR codes will surely enhance your branding and appeal to your audiences.

Here are a few short tips on how you can enhance your QR code’s looks and create your own stunning designer QR codes.

1. Add colors to your QR codes. They don’t always have to be black and white. You can add colors as long as you maintain proper contrast between the dark foreground and light background.
2. Soften it with rounded corners. Softening the corners will dramatically reduce the visual stiffness of QR codes. Soften it and see the difference.
3. Use other graphic elements to add dimension to your QR codes. You can add images or any design element like your logo on your QR code. Just make sure you don’t obstruct some of the important boxes that contain data.
4. Use trial and error. You might ask on the previous tip, how do I know which of my QR code blocks I can mess around without affecting code readability. Well, technically you can do the math to compute which blocks aren’t necessary and can be played around or removed. But doing computations like that is unnecessary, you can just do your design, scan and test it as you go along.

Be sure to try different code readers when you're done. The more reader that can "read" your design, the lower the chances of people having errors reading the QR :)

Below are some samples i got from the web. The sky is the limit when you have imagination & dedication :)

p/s: credits goes to the reviewers & designers of the QR codes above :P